For decades, constructing any sort of large-scale affordable housing development on Native American land was nearly impossible. Then California changed the rules—and now, the whole country may follow.

The Low-Income Housing Tax Credit program, the country's largest program for building and preserving affordable rental housing, was virtually inaccessible to California's Native American tribes until a few years ago.

"The way that affordable housing is built most effectively across the United States is by using the Low-Income Housing Tax Credit program," said Elizabeth Glynn, CEO of Travois, a consulting firm that facilitates housing and economic development on reservations across the country. "California, unfortunately, has made it nearly impossible to access those credits."

The 9 percent and 4 percent tax credits, which developers sell to private companies, have generally provide a chunk of financing to any income-restricted, multi-unit project that's gone up in the past few decades. In total, about $8 billion in tax credits are dished out each year, over $2 billion of which goes to California.

But from 1986, when the program started, through 2013, not a single one of those credits went towards building housing on any of the state's 100 reservations and rancherias.

Tribes simply could not compete in the application process, Glynn said, which tends to favor developments that are near transit, community resources, and are easier to complete.

"Instead of being able to build a multi-unit apartment building, they have to start by putting in sewer systems, sidewalks, roads," she said.

The lack of building has not been for lack of need, said Cliff Oneill, executive director of the Quechuan Housing Authority on the Fort Yuma Indian Reservation in Imperial County.

"Homes here were built 40, 50 years ago," he said. "They're very old and it's a constant job for us to maintain them."

Overcrowding, too, is an issue.

"In some cases, we have 12, 13 people living in one house," he said.

A study commissioned by the California Department of Housing and Urban Development in 2015 found nearly a third of people on tribal lands are living below the poverty line in California. Rates of housing overcrowding are higher than elsewhere in the state. And 8.4 percent of occupied units on tribal land lacked complete plumbing, while 6.5 percent lacked complete kitchens. Both numbers are miles above the rest of the state.

The tribal areas did and do receive some funding from the U.S. Department of Housing and Urban Development. Oneill said it's mostly spent on maintaining existing housing.

"We only had sufficient funds to build one, sometimes two homes per year," Oneill said.

Then in 2014, recognizing the need, the California Tax Credit Allocation Committee started issuing a minimum of $1 million of the state's roughly $1 billion in low-income housing tax credits to tribal lands. Since then, at least five developments on tribal lands have been funded, including a 44-unit project on the Fort Yuma Indian Reservation.

"It's an excellent source of revenue and it allows us to build quality homes for our members," Oneill said.

Now, legislation making its way through Congress would force all states to consider the needs of tribal lands when allocating low-income housing tax credits. The proposed change is a piece of a larger set of reform bills taking shape as Congress gears up to tackle a potential tax code overhaul. And the proposed changes would benefit low-income renters all over California.

U.S. Senator Maria Cantwell (D-WA) and Senate Finance Committee Chairman Orrin Hatch (R-UT) have introduced S 548, which would reform the tax credit as well as expand it by 50 percent over five years. House bill HR 1661, introduced by Rep. Patrick Tiberi (R-OH) and Rep. Richard Neal (D-MA), is largely similar, but does not call for expansion.

Affordable housing advocates around the state are keen on seeing the reforms go through.

"We're trying to make sure we can use the credit in a wide range of types of communities," said Emily Cadik, who advocates for affordable housing funding on Capitol Hill for Enterprise Community Partners.

In Los Angeles County, current rules have limited companies' ability to develop affordable housing in many poor neighborhoods. Under current law, developments in census tracts with high poverty rates can receive additional funding to help with construction of community facilities like child care centers. But the number of census tracts that can qualify in any one area is capped, so nearly 1,000 of L.A.'s neighborhoods have met income criteria for the extra investments, but haven't been eligible, said Peter Lawrence, director of policy and government relations for Novogradac & Co., an accounting firm specializing in low-income housing tax credits.

"That can often be the difference between a project penciling out and not," he said.

Los Angeles and Puerto Rico, he said, have the highest number of high-poverty areas that are not been eligible for such funding. The Senate and House bills would both raise the number of census tracts that can get it.

Advocates in rural areas of the state, too, are excited about potential reforms, particularly the Senate bill's proposed expansion of the credit.

"Our housing stock is in high demand, rents are increasing," said Ryan LaRue, who heads development for Rural Communities Housing Development Corporation. Mendocino County, where the firm is located, has one of the highest per-capita homelessness rates in the country.

Affordable housing, he said, is an issue in California, whether it's rural, urban or tribal land.